bug#4547: a bug: emacs 23.1: very large font

bug#4547: a bug: emacs 23.1: very large font

[Daniel Novotny]

Hello,

we upgraded Emacs in Fedora 11 and 12 to 23.1, but users start complaining,
that the font is too large.

this is a screenshot from cleanly installed Fedora 12 Alpha, showing
the default font:

http://people.fedoraproject.org/~dnovotny/emacs-fonts-large.jpg

do you know, what can be done to obtain the same
font size as before? This is a screenshot from Fedora 10:

http://people.fedoraproject.org/~dnovotny/emacs-fonts-normal.jpg

the bug report implies that the problem here is that emacs is scaling the requested font size according to
the display resolution reported by Xorg. These are accurate for the dimensions of the screen, but that
doesn't mean emacs should use them to change the font sizes the user requested:
see https://bugzilla.redhat.com/show_bug.cgi?id=517272#c3

thank you for your ideas,

  Daniel Novotny, Red Hat inc.

bug#4547: a bug: emacs 23.1: very large font

[Kenichi Handa]

In article <487180556.521141253786336982.JavaMail.root@zmail04.collab.prod.int.phx2.redhat.com>, Daniel Novotny <dnovotny@redhat.com> writes:

> the bug report implies that the problem here is that emacs is scaling the requested font size according to
> the display resolution reported by Xorg. These are accurate for the dimensions of the screen, but that
> doesn't mean emacs should use them to change the font sizes the user requested:
> see https://bugzilla.redhat.com/show_bug.cgi?id=517272#c3

That bug report says:

> eg, my laptop display reports xdpyinfo 
> 
>   dimensions:    1600x1200 pixels (304x228 millimeters)
>   resolution:    134x134 dots per inch
> 
> while my external monitor report
> 
>   dimensions:    1680x1050 pixels (514x321 millimeters)
>   resolution:    83x83 dots per inch
> 
> Now both of these are accurate for the dimensions of the screen, but that
> doesn't mean emacs should use them to change the font sizes the user requested
> 
> > For example, using my laptop display
> > 
> >  - Go to the menu 'Options -> Set Default Font'.
> >  - Select  'DejaVu Sans Mono, Book, 12pt'
> >  - In a buffer, move cursor over a letter, and type  'c-u c-x =', and it
> > displays
> > 
> >     xft:-unknown-DejaVu Sans-normal-normal-normal-*-22-*-*-*-*-0-iso10646-1
> > (#x50)
> 
> ie, so when user requested requested 12pt, and emacs instead gave them 22pt

At least, this bug report confuses point and pixelsize.  In
the above case, Emacs selected "22-pixelsize" font, not
"22-point" font.  And, on 134 DPI screen, 22-pixel is
12-point (3.4mm).  So, it should be the correct size the
user requested by saying "12pt".

If one wants a font of 12-pixelsize, do something like:

ESC : (set-default-font "dejavu sans mono:pixelsize=12") RET

---
Kenichi Handa
handa@m17n.org

bug#4547: a bug: emacs 23.1: very large font

[Jan Djärv]

While not technically a bug, it is unfortunate that Emacs uses a DPI value 
other than the rest of the applications.

In Emacs CVS (i.e. the upcoming Emacs 23.2 release), Emacs looks at the DPI 
setting from XSETTINGS and uses that. That should make Emacs looks the same as 
other applications.

	Jan D.

bug#4547: a bug: emacs 23.1: very large font

[Stefan Monnier]

> While not technically a bug, it is unfortunate that Emacs uses a DPI value
> other than the rest of the applications.

The main problem I see is that Emacs tries to choose a default font such
that it will always have the same physical screen size.

This seemed like a good idea at some point in time, but experience shows
that with higher DPIs, the smoother curves of letters makes the text
more legible at the same physical display size, so people are happy to
use slightly smaller fonts (in other words, small fonts used to be
illegible not just because they were physically small but also because
there weren't enough pixels to make them legible).

So choosing a fixed physical size is not really a good idea.

Another reason why this is, is that what "really" matters is not the
dimension of text on the physical screen, but the "apparent size" seen
from the user, which is approximately "screen-size /
distance-from-the-eye".  And it turns out that the distance between the
eye and the screen depends on the device being used.

For all these reasons, the real physical DPI is not an ideal basis to
choose the default font size.  So using some kind of user-controlled
"perceived DPI" would be a much better choice.  IIUC the DPI provided by
Xsettings is a good choice for that.


        Stefan